Light guide for coupling light output from a light source to the skin

ABSTRACT

An Intense Pulsed Light apparatus for cosmetic or therapeutic treatment of the skin having a light source is provided with a light guide having an entry face in a rigid light guide component and an exit face in a flexible light guide component adapted to conform to highly curved parts of the body of a patient.

This application is the National Phase of International ApplicationPCT/EP01/07926 filed 10 Jul. 2001 which designated the U.S. and thatInternational Application was published under PCT Article 21(2) inEnglish. This application also claims priority to Great BritainApplication No. GB 0017051.4 filed 11 Jul. 2000, which document isherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved light guide for couplinglight output from a light source to the skin, especially to relativelysteeply curved areas of the skin. Light guides are described which aresuitable for use in cosmetic or therapeutic light treatment apparatus.

2. Description of the Related Art

Apparatus for such use will have a light source capable of a lightoutput sufficient to produce the desired effect when properly directedto the skin of the patient. The light source is typically either a laseror a high intensity flash or continuous source of non-coherent light. Inmost laser systems the light is directed to the skin by transmissionthrough air without the use of a light guide. In most non-coherent lightoperated systems (also known as Intense Pulsed Light or IPL System)however, and in some laser systems, the light is transmitted to the skinvia a solid light guide which has a light-entry face adjacent the lightsource and a light exit face which contacts the skin.

Light guides of various shapes are shown in EP-A-0885629, DE-A-3803763,and U.S. Pat. No. 5,620,478. For optical transmission, and skin cooling,it has been proposed to put a gel between the light guide and the skin.Typically, the light guide is a short block of transparent, rigid, solidmaterial which has a flat or curved skin contacting face. Materials usedinclude glass, sapphire, and plastics. One of the advantages ofnon-coherent light operated systems over laser systems is that it ispossible to obtain a suitable light energy flux over a larger area. Thisreduces treatment time and makes it easier to achieve a uniform lightexposure over a large area. However, we have found that whilst theexisting rigid light guides are satisfactory in use on relatively ‘flat’areas of skin, they are less satisfactory when treatment is aimed atrelatively highly curved areas of the body, such as the face. Thedifficulty in treating the face is made more severe by the skin beingcurved in more than one direction and by the underlying bone structurewhich prevents the skin being flattened by application of pressure viathe light guide.

Failure of good contact between the light guide and areas of the skincan lead to untreated areas or possibly to small burns. The latterappear to result from the light energy which should penetrate downthrough the skin instead being absorbed in the skin surface layers.Possibly this is due to light rays impinging on the skin at a low angleof incidence.

SUMMARY OF THE INVENTION

The present invention now provides light guide for guiding light from alight generating apparatus to the skin of a patient, said light guidehaving a light-entry face and a light-exit face, and said light-exitface being deformable to conform its shape to the skin.

The light guide may be designed as an attachment for a pre-existingdesign of IPL apparatus. Especially one as described in EP 0885629.

Preferably, the light guide incorporates a material which absorbs lightwith wavelengths greater than 950 nm or from 750 nm for someapplications e.g. skin rejuvenation treatment of vascular lesions,wrinkle removal or acne treatment. Generally, wavelengths in the rangeof 750 to 950 nm are relatively inefficient in such uses but have someeffect and may be useful if the power available from the light source inthe wavelengths up to 750 nm is not sufficient.

Preferably also, the light guide incorporates a material which transmitslight within the wavelength range between 400 nm and 750 nm or from 400nm to 950 nm absorbing no more than 10 percent of the energy ofwavelengths within the respective range.

Particularly for use with a substantially monochromatic light sourcesuch as a laser, the light guide may be such as to transmit the lightemitted by the light source whilst absorbing no more than 10% of itsenergy. The combination of a laser light source with a transmissive, lowattenuation, flexible light guide provides increased efficiency ofcoupling of the laser light into the skin and allows blood to be pressedaway from the treatment site. This reduces the amount of light energywhich is lost by absorbance by the blood. The wavelength of the lightsource may be chosen to be appropriate for the selected treatment.

One option within the invention is that said light-exit face bounds afluid filled chamber. Said fluid may be a gel. Preferably then, saidfluid is a material having the light absorption and/or transmissionproperties given above.

Such a light guide preferably comprises an inlet for said fluid and anoutlet for said fluid, whereby in use said fluid may be circulatedthrough the chamber to allow for cooling of the fluid outside of thechamber. The cooled fluid may then serve to cool the skin to which theapparatus is applied in use.

Alternatively, said light-exit face may bound a body of deformable solidmaterial.

Preferably, the light guide, especially the flexible components of thelight guide (fluid containing envelope, gel or fluid contained thereinand/or flexible solid material), is or are such as to absorb at least50%, more preferably more e.g. 90% of the light having wavelengths above950 nm, more preferably at least 90% of the light having wavelengthsabove 750 nm.

There is further provided apparatus for producing light pulses forapplication to the skin, said apparatus comprising a light source, whichpreferably is adapted to produce pulses of light, and a light guidepositioned to receive light from the light source and to transmit thelight to the skin of a patient, wherein said light guide is a lightguide according to the invention as described above.

Preferably, the light source and said light guide are adapted to produceand transmit to the skin light pulses of an intensity sufficient toproduce a cosmetic or therapeutic effect selected from the groupconsisting of depilation, coagulation of small blood vessels, increasedproduction of skin collagen, skin rejuvenation, photodynamic therapy,tattoo removal and the treatment of acne, psoriasis, warts, vasculartrauma, skin cancer, telangiectasis, capillary hemangioma, port winestains or birthmarks, other vascular or pigmentation malformations inthe skin. Such apparatus may thus be used for the treatment of wrinklesor sun damage. effects in the skin and uneven pigmentation.

Preferably the apparatus is adapted to produce a light output energy onthe skin of up to 30 J/cm², e.g. from 3 to 26 J/cm², or 25 J/cm² ormore. Alternatively, or additionally, the apparatus may be adapted toproduce an output energy on the skin of from 3 to 10, e.g. 5 to 7 J/cm²,especially for collagen remodelling.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described and illustrated with referenceto the embodiments shown in the accompanying drawings in which:

FIG. 1 is a schematic side view of a first apparatus according to theinvention;

FIG. 2 is a schematic side view of a second apparatus according to theinvention;

FIG. 3 is a schematic side view of a third apparatus according to theinvention; and

FIG. 4 is a schematic side view of a fourth apparatus according to theinvention.

DETAILED DESCRIPTION

As shown in. FIG. 1, a first embodiment according to the inventioncomprises a light source 10, which may be a laser or non-coherent lightsource such as a flash lamp. Light from the light source 10 is emittedinto a rigid light guide 12, which may be of glass or any material knownin the art for this purpose.

Light transmitted through the rigid light guide 12 enters a flexiblelight guide 14 comprising a flexible outer envelope 16 containing awater based gel or demineralised water 18 or else being a unitaryconstruction and made from a flexible light transmitting material.Examples of suitable materials include silicone rubber. The water basedgel or water or the said flexible material may if desired be coloured bythe inclusion of a suitable dye to filter out undesired wavelengths oflight.

The light guide 14 is shown being applied to a schematically illustratedhighly curved part of the body 20 against which it at leastapproximately conforms.

In FIG. 2, an alternative embodiment is shown in which the gel 18 isomitted. Inlet conduit 22 and outlet conduit 24 which enter and leavethe envelope 16 are used to pass a cooling liquid such as water throughthe interior space of said envelope to a cooling station from which theliquid is recirculated to the envelope 16.

In each case, the rigid light guide 12 with the deformable light guide14, or the deformable light guide 14 taken alone, constitutes a lightguide according to the first aspect of the invention.

The materials used for the flexible light guide 14 may be chosen to besufficiently stiff to ensure a reasonably well defined light output areabut sufficiently soft and flexible to conform well with the target area.The side walls of the flexible light guide may be made more stiff thanthe light exit face.

FIGS. 3 and 4 show modified versions of FIGS. 1 and 2 respectively inwhich the sides of the flexible light guide 14 are supported by a rigidtube 15, which may be of material which is reflective on its inner facesuch as mirror polished metal (e.g. Al) or plastics such as SPECTRALON™.This is especially desirable where the material 18 filling the envelope16 is of low viscosity, e.g. when it is water.

The envelope 16. may be of plastics material or rubber latex.Preferably, it has a low optical attenuation. PVDF (polyvinylidenefluoride) has been found suitable as is absorbs only 1.6% of the lightwhen used in a suitable thickness to provide the required structuralintegrity.

The embodiments described are especially useful in treating the highlycurved areas of the face and neck in wrinkle removal and skinrejuvenation.

1. A light guide for guiding light from a light generating apparatus tothe skin of a patient, said light guide having a light-entry face and alight-exit face, and said light-exit face being deformable to conformits shape to the skin, wherein between the light-entry face and thelight-exit face said light guide comprises a material which attenuateslight with wavelengths greater than 950 nm.
 2. A light guide as claimedin claim 1, which attenuates light with wavelengths greater than 750 nm.3. A light guide as claimed in claim 1, which transmits light within thewavelength range of 400 to 950 nm absorbing no more than 10 percentthereof.
 4. A light guide as claimed in claim 3, which transmits lightwithin the wavelength range of 400 to 750 nm, absorbing no more than 10%thereof.
 5. A light guide as claimed in claim 1, which transmits lightat a wavelength appropriate for at least one cosmetic or therapeutictreatment absorbing no more than 10% of said light.
 6. A light guide asclaimed in claim 1, wherein said light-exit face bounds a body ofdeformable solid material.
 7. A light guide for guiding light from alight generating apparatus to the skin of a patient, said light guidehaving a light-entry face and a light-exit face, and said light-exitface being deformable to conform its shape to the skin, wherein saidlight-exit face bounds a fluid filled chamber.
 8. A light guide asclaimed in claim 7, comprising an inlet for said fluid and an outlet forsaid fluid, whereby in use said fluid may be circulated through thechamber so as to allow cooling of the fluid outside of the chamber.
 9. Alight guide as claimed in claim 8, wherein said fluid is water. 10.Apparatus for cosmetic or therapeutic intense pulsed light (IPL)treatment, said apparatus comprising a light source and a light guidepositioned to receive light from the light source and to transmit thelight to the skin of a patient to produce cosmetic or therapeuticchanges therein, wherein said light guide has a light-entry face and alight-exit face, and said light-exit face is deformable to conform itsshape to the skin, wherein said light guide light exit face bounds afluid filled chamber, further comprising a cooling unit connected in aflow circuit with said fluid filled chamber via an inlet and an outlet,for cooling said fluid.
 11. Apparatus as claimed in claim 10, whereinthe light source and said light guide are adapted to produce andtransmit to the skin light pulses of an intensity sufficient to producea cosmetic or therapeutic effect selected from the group consisting ofdepilation, coagulation of small blood vessels, increased production ofskin collagen, skin rejuvenation, photodynamic therapy, tattoo removaland the treatment of psoriasis, vascular trauma, telangiectasis,capillary hemangioma, cancerous cells, port wine stains or birthmarks.12. Apparatus as claimed in claim 10, adapted to produce a light outputenergy density on the skin of 25 J/cm² or more.
 13. Apparatus as claimedin claim 10, adapted to produce a light output energy density on theskin of up to 30 J/cm².
 14. Apparatus as claimed in claim 13, adapted toproduce a light output energy density on the skin of from 3 to 26 J/cm².15. Apparatus as claimed in claim 10, wherein said light source is amonochromatic light source and said light guide transmits light at thewavelength of the light source absorbing no more than 10% of said light.16. Apparatus as claimed in claim 15, wherein said light source is alaser.
 17. Apparatus for cosmetic or therapeutic intense pulsed light(IPL) treatment, said apparatus comprising a light source and a lightguide positioned to receive light from the light source and to transmitthe light to the skin of a patient to produce cosmetic or therapeuticchanges therein, wherein said light guide has a light-entry face and alight-exit face, and said light-exit face is derivable to conform itsshape to the skin, wherein between the light-entry face and thelight-exit face said light guide comprises a material which attenuateslight with wavelengths greater than 950 nm.
 18. Apparatus for cosmeticor therapeutic intense pulsed light (IPL) treatment, said apparatuscomprising a light source and a light guide positioned to receive lightfrom the light source and to transmit the light to the skin of a patientto produce cosmetic or therapeutic changes therein, wherein said lightguide has a light-entry face and a light-exit face, and said light-exitface is deformable to conform its shape to the skin, wherein between thelight-entry face and the light-exit face said light guide comprises amaterial which attenuates light with wavelengths greater than 750 nm.19. Apparatus as claimed in claim 17, wherein said light guide transmitslight within the wavelength range of 400 to 950 nm absorbing no morethan 10 percent thereof.
 20. Apparatus as claimed in claim 17, whereinsaid light guide transmits light within the wavelength range of 400 to750 nm absorbing no more than 10 percent thereof.